The invention relates generally to methods of and apparatus for solid material remediation, using heat energy for the volatilization, disassociation and detoxification of contaminants. More particularly, the invention relates to methods of and apparatus for solid material remediation, using hot gases to adsorb and drive contaminants from the solid materials, and then to subject the hot gases including the contaminants to further heating to break down and detoxify the contaminants, such as by oxidation. These processes and related apparatus have been used to decontaminate soil which has become contaminated by, for example, oil or gasoline spills.
Various types of apparatus and methods are known, all of which perform a similar function, namely to first volatilize contaminants and then heat the contaminants to break down the molecular structure and to oxidize the contaminants before the exhaust is emitted into the atmosphere. Thus, in general, a decontamination procedure includes two steps. First, the contaminants, in most instances hydrocarbons, are volatilized and thereby removed from the solid materials. In a second series of steps, the volatilized contaminants need to either be removed from the gaseous carrier medium or they need to be chemically altered into environmentally acceptable compounds. Some contaminants may require scrubbers, which are known and available. Generally, though, in the case of the contaminants being hydrocarbons, the volatilized contaminants are burned in a high temperature process to form non-objectionable carbon dioxide and water vapor.
Much effort has already gone into improving this general process to bring down the cost of remediation of solid material contaminated with hydrocarbons. It appears that more effort in development and further improvements are needed in the technological field of soil remediation. As long as gasoline and fuel oils remain a major source of energy for our society, oil spills tend to remain a constant threat to the environment. Since soil typically has a certain moisture content, removal of hydrocarbons by heat becomes more complicated by a concurrent vaporization of water and associated cooling of the material to be decontaminated. Also, hydrocarbon contamination may contain a mixture of lighter, short-chain and heavier, long-chain hydrocarbons. The lighter hydrocarbons may volatilize at a temperature at or below that at which water contained in the material to be decontaminated forms steam. Thus, lighter hydrocarbons may be removed with water vapor and may need to be separated from the water vapor. Heavier, long-chain hydrocarbon fractions are not so readily volatilized and need to be separated from the soil material at temperatures well above those at which water is boiled off from the soil. Two steps of soil decontamination have in the past required apparatus which is complex and comparatively costly to transport, set up and maintain. Improvement in efficiency of cleaning up oil spills may be brought about by improvements in any of a number of ways. Cost reduction may result from a simplification of known decontamination apparatus. The cost of transporting apparatus to a site may be improved by making the remediation equipment more compact. The efficiency of removing hydrocarbons from bulk material may further become improved by an increase in throughput capacity of a soil remediation apparatus, or by a decrease in an energy requirement to process a given amount of contaminated material.